Search This Blog

In my last post about creating an Appharbor notification bot, I described about the problem domain, the solution approaches and how the end to end scenario works.This post would dig deeper into the implementation aspects of the solution.

To start with we need to understand the two esential ingredients for this recipe

Appharbor Service hooks: Appharbor Service hooks are the building block for the solution. Appharbor provides capability, where it can post to any public url with status of a build on completion. Service hooks are available for events

Build Success.

Build failure.

XMPP protocol: XMPP is a protocol used for Instant Messaging (IM) communication. It allows us to relay messages to the users IM client using XMPP servers (in our case Google Talk messaging servers).

With the understanding on these two concept we are ready to dive into the nitty gritty of the solution.

Assuming that the user did the initial configurations to setup notifications (see my earlier post), here is what happens behind the scenes when a build notification is triggered from Appharbor

One may find it odd that parts of the solution are hosted on AppHarbor and parts on Windows Azure worker role.

The reason for this was, inability for IIS to host the XMPP client and allow it to keep persistent connections to XMPP server. Whenever i was trying to instantiate a XMPP client (agsXMPP) the call silently failed when hosted in IIS. In a console app it worked fine. I did not dwell much into the issue but based on my initial research the XMPP client tries to create a persistent connection to XMPP server (in our case Google Talk) but IIS does not allow this.

Since AppHarbor provide more of a web endpoint (presumably in IIS) the solution did not work when hosted in AppHarbor(even in Azure webrole). I had to create a Azure Worker Role and expose a web endpoint from the worker role. Using ASP.Net Web APISelf hosted feature, I was able to host a http endpoint within the worker role, but it did require some configuration changes for the worker role.

To know more about the implementation details look at the source code available on GitHub.

Comments

Popular posts from this blog

I was helping on a Windows Phone application where the requirement was to cache the images the phone downloads on the isolated storage for offline viewing.
I wanted a solution which was simple and as transparent as possible. While researching I found someone wrote a Silverlight converter for loading images from isolated storage. Taking that as a base I created a converted which canLoad image from web (http + https), and persist it to isolated storage.In case of network connectivity issues can load the same image from isolated storage. It does that by mapping the http url to a isolated storage location.In case the network is down and the image is neither there in cache, loads a default image, passed as parameter to converter.Here is the gist for the implementation.

To use the converterImport the name space.Declare the converter as resource.Set the Image Source Property to use this converter like this

If you play around with IIS Url Rewriting rules and try to do redirects on an HTTP POST you loose your POST data.

To make sure you get the post data you have to set the `redirectType` to `Temporary` within your rules. So the action configuration looks like this

<action redirectType="Temporary" type="Redirect" url="http://{HTTP_HOST}{REQUEST_URI}"> </action>
You may think what scenario warrant a POST request redirect. We faced one such scenario while doing SSO with a federated Identity Provider (IP) such as Google, Azure AD. In federated authentication scenario once the user is authenticated by the IP, it redirects back to your site with claim tokens in a POST request over secure channel (https). In our case we wanted to redirect to user back http after receiving the request. But any redirects were causing loss of token. By doing a 307 (Temporary) redirect we were able to preserve the post data.